#include <stdio.h>
int main()
{
    int a, b, time;
    scanf("%d%d", &a, &b);
    time = b / 100 * 60 + b % 100 - (a / 100 * 60 + a % 100);
    printf("%.2d:%.2d", time / 60, time % 60);
    return 0;
}